This Buy American/ARRA compliant backup power supply has been tested and certified to meet the National Electric Code, UL and cUL requirements for factory and field installation. This unit features the latest in Polymer Lithium-Ion battery technology providing longer cycle life, high energy density and zero memory effect as well as a test switch and charge indicator panel. The unit does not affect normal light fixture operation and can be used with switched or un-switched lighting fixtures. This emergency power supply is safe, environmentally friendly and highly reliable providing 90 minutes of automatic emergency lighting in the event of a power failure. The unit automatically returns to charging mode when power is restored and reaches full capacity within 24 hours.